Each day, in order to compute the most recent UTGPS estimate available, the UTGPS algorithm integrates forward from a past date up through the previous day. Some of the input data the algorithm had used in previous runs to determine UTGPS for earlier epochs may have been updated since those runs. Thus, when estimating the most recent UTGPS value, UTGPS estimates for previous epochs may be altered slightly as well. The UTGPS value for a given epoch may continue to change slightly for a week or so after its first posting.